The present invention relates to voltage regulators for vehicles, and more particularly the invention relates to a voltage regulator for vehicles having an initial excitation function and a generation indicating function.
There is known in the prior art a type of vehicle voltage regulator having an initial excitation function for the generator and also incoporating a generator power generation indicating function to meet the requirement for a reduction in the size. However, this type of voltage regulator has been so designed that the detection of the generated output of the generator for the control of initial excitation and that for the control of generation indication (the indication is effected by turning on an indicator lamp for the time interval between the closing of the ignition switch and the time that the generated voltage of the generator reaches a predetermined value) are accomplised by means of separate circuit. However, the detection of generated output for the control of initial excitation and that for the control of generation indication are related to each other and also it is desirable to effect the detection by a common detecting circuit for the purpose of reducing the size of the voltage regulator.
A common detecting circuit of this type has been proposed in which the output voltage of the generator is detected with respect to a predetermined reference voltage so that when the output voltage is lower than the reference level, it is determined that the generator is not generating so that the generation indicator lamp is turned on and the excitation current for initial excitation purposes is continuously supplied to the field winding, whereas when the output voltage is higher than the reference level, it is determined that the generator is generating so that a change-over from the initial excitation to the full excitation is effected and simultaneously the generation indicator lamp is turned off. Also, in this case, both the change-over from the initial excitation to the full excitation and the turning off of the generation indicator lamp are effected on the basis of the same level of the generated voltage, thus giving rise to the following disadvantages. In other words, in order to effect the change-over from the initial excitation to the full excitation, in view of the rising of the generated voltage of the generator, during the starting period the rotational speed of the generator must for example be 1,000 rpm so that at that time the output voltage peak value (at the terminal P of the generator) becomes 2 to 3 V and thus it is only necessary to detect the level of 2 to 3 V and thereby to effect the control. On the other hand, in order to effect the control of generation indication, even if the generator stops generating due to the interruption of the current flow in the field winding caused by such abnormal condition as a break or short-circuiting of the generator field winding, for example, the residual magnetism or the like causes a certain output voltage (e.g., about 3 V at 6,000 rpm and about 4.5 V at 10,000 rpm), so that the generation indicator lamp is turned off and the proper generation indicating function is not performed. This also results in loss of the abnormality warning function for informing the occurrence of such faulty condition.